1. Field of the Invention
This invention relates to medical equipment, and more particularly, to an anesthetic applicator with a temperature/moisture regulating capability which is capable of regulating the anesthetic gas being supplied to the patient at suitable temperature and humidity levels. This allows the supplied anesthetic gas to adjust to the temperature/moisture conditions of the patient's body, so that undesirable consequences to the patient can be avoided.
2. Description of Related Art
When performing an operation on a patient, an essential step is to apply anesthetic gas (typically mixed with nitride oxide and oxygen) to the patient. In doing this, the physiological conditions of the patient should be considered carefully so as to apply the anesthetic gas in a suitable manner to avoid undesirable consequences to the patient.
Normally, when general anesthesia is to be administered to the patient, the application thereof is usually performed by inhaling. However, it is a drawback of the conventional way of applying anesthetic by inhaling that they require the anesthetic being applied to be significantly greater in volume than the breathable volume of the human body i.e., greater than 5,000 cc/min. Moreover, the exhaled breath from the patient is directly exhaled to the ambient atmosphere causing air pollution. The conventional semi closed-cycle anesthetic application method can reduce the amount of the anesthetic being used. However, since the degree of anesthetic state of the patient is uncertain, an additional amount of anesthetic should be applied in accordance with the blood pressure of the patient. The problem of the likelihood of over application of the anesthetic still exists. The recently widely used closed-cycle anesthetic application method employs a closed-cycle loop that can recycle the exhaled anesthetic from the patient to be reused again on the patient. In this method, a large quantity of anesthetic is initially applied to the patient until the patient reaches the desired degree of anesthetic state; and after this, the applied anesthetic is reduced in quantity until only oxygen is supplied to the patient for breathing. The closed-cycle loop allows the applied anesthetic to be contained in a closed space so that the environmentally-unfriendly nitride oxide (N.sub.2 O) will not be exhaled into the atmosphere.
Beside the foregoing, further problems exist in the application of anesthetics by conventional methods. Namely, after the anesthetic gas has been inhaled by the patient, it will be warmed up and moisturized after passing through the nostrils of the patient to a temperature of about from 34.degree. C. to 37.degree. C. and an absolute humidity level of about 36 mg H.sub.2 O/L to 45 mg H.sub.2 O/L under conditions of a relative humidity of 100%. In the inhalation anesthetic application method, since ducts are used to direct the anesthetic into the body of the patient, the anesthetic would not be warmed up and moisturized by the nostrils. This would result in the undesired consequence of the anesthetic gas received by the lung of the patient being relatively cool and dry, with a temperature that can be lower than 28.degree. C. and an absolute humidity level that can be below 26 mg H.sub.2 O/L. Thus, the dry anesthetic gas could cause harm to the tissues of the respiratory organs. Moreover, since the operating room is usually maintained at a temperature of about 20.degree. C., the supplied anesthetic gas is also substantially at this temperature level which is significantly lower than the body temperature of the patient. As a consequence, the patient could suffer from a decrease in body temperature that may significantly weaken the patient's capability to recover from the operation. The risk of the operation is thus high.
Various costly methods can be used to maintain the body temperature of the patient, such as electric blankets or heated-water pads. Alternative methods include the regulating the supplied anesthetic gas at a suitable temperature and a suitable humidity. However, conventional means of regulating temperature/humidity for anesthetic gas are quite unsatisfactory and inconvenient to use and could easily harm the patient. For instance, in the HME, which was introduced in the 1980s, when the flow rate of the anesthetic gas is low, a low temperature of the gas may also occur. Recently, a new temperature/humidity regulating means using a coaxial tube structure has been introduced, where an inner tube supplies anesthetic gas to the patient and an outer tube receives and recycles the exhaled anesthetic gas from the patient. The exhaled anesthetic gas is normally higher in temperature than the anesthetic gas in the inner tube supplied to the patient. Thus, ideally, when the exhaled breath from the patient passes through the outer tube, it can warm up the anesthetic gas in the inner tube so that the anesthetic gas supplied to the patient can be raised to a temperature level substantially equal to the body temperature of the patient. However, since the ambient temperature in the operation room is relatively low, the heat of the exhaled anesthetic gas can quickly dissipate, thus, the effect of warming up the supplied anesthetic gas is limited.
There exists, therefore, a need for a new anesthetic applicator with temperature/humidity regulating capability that can maintain the supplied anesthetic gas at suitable temperature and humidity levels to facilitate medical and surgical operations.